Photovoltaic concentrators are known in the industry as high concentration photovoltaic (HCPV), medium concentration photovoltaic (MCPV) and low concentration photovoltaic (LCPV). These concentrators operate mostly with a dual axis tracker to point the apparatus toward the sun. Photovoltaic cells comprising of semiconductor junctions as p-n junctions are used. It is well known that light with photon energy greater than the band gap of an absorbing semiconductor layer in a semiconductor junction is absorbed by the layer. Such absorption causes optical excitation and the release of free electrons and free holes in the semiconductor. Because of the potential difference that exists at a semiconductor junction (e.g., a p-n junction), these released holes and electrons move across the junction in opposite directions and thereby give rise to flow of an electric current that is capable of delivering power to an external circuit. As such photovoltaic cells offer a source of renewable energy, as once installed all they require is the sun to generate electricity. Unique potential of concentrated photovoltaic technology is made aware by the present LCPV invention.
LCPV systems are advantageous because they do not generate excessive heat at the photovoltaic cells; therefore they do not require active cooling by heat transfer fluid. Cooling of the solar panel with a passive heat sink is only needed.
It is apparent that current commercial developments such as driven by the National Solar Technology program under the US Department of Energy for PV cells and panels are focused to the cost reduction of the semiconductor photovoltaic cells and wafers together with their encapsulation, interconnection, etc.
Silicon PV cell wafer thickness is decreased from the standard 0.3 mm (300 μm) to reduce cell cost. However, it would be apparent that increasing the area of the PV cells whilst increasing the electrical power of the solar assembly does so with a cost that is approximately linear to the output, as this is essentially linear with area of the PV cells, silicon used, packaging materials, assembly, etc. Accordingly it would be beneficial to provide an increase in electrical power output for a given area of PV cell, and thereby lower costs both in the near-term and when large-volume production of PV cell technologies (such as crystalline silicon cells and multi-junction cells) is reached. The so-called concentrating photovoltaic, due to immediate and long-term benefits, has inspired substantial venture capital investment in CPV in recent years. The concentrator developments leverage work done for PV cells and concentrating thermal technologies for providing heating to buildings or generating electricity through turbines driven by heated liquid/gas systems. However, challenges for these CPV approaches include additional complexity, a much smaller market presence, and a very limited history of reliability/field-test data.
Recently the total installed CPV capacity is less than 1 MW in the United States and only a few MWs worldwide, virtually all using non concentrating silicon PV cells. Thus, the fundamental challenge of CPV is to lower cost, increase efficiency, and demonstrate reliability to overcome the barriers to entry into the market at a large scale. These challenges must all be addressed at the system level and include:                System-Level Design, where PV cell, optical train, and tracking must be engineered not only to work together but need to be designed for manufacturability, as well as cost, with attention given to tolerance chains, automation, scalability, and ease of assembly, maintenance;        Reliability, where factors specific to conventional prior art CPV systems include the high-flux, high-current, high-temperature operating environment encountered by the cells; weathering and other degradation of the optical elements, the mechanical stability of the optical train, and the operation of the mechanical parts of the tracking systems;        Cost, where PV cell cost is a substantial fraction of the total system cost but further reduction may be achieved with increased power output and reduced costs for the mechanical and thermal aspects of the solar power generator. Such approaches to lowering the cost of the system include system design for reducing required tracking accuracy, as well as refined an simpler mechanical engineering of the tracker, designing optical trains that are compatible with techniques for inexpensive, robust fabrication of what may in some designs be sophisticated optical surfaces, and provision of low cost thermal management solutions; and        Efficiency, as improved efficiency is a direct way to lower the cost of the system and the area required to host a system for given power output; the area can have a significant effect on cost of electricity in most systems. As with cost and reliability, efficiency must be addressed at the system level to reduce parasitic losses so that systems can realize their potential efficiencies. Higher electrical output from a given area of solar flux input means higher efficiency.        
Considering firstly the tracking system a variety of prior art techniques have been reported including polar, horizontal axle, vertical axle, two-axis altitude-azimuth, and multi-mirror reflective altitude-azimuth. For large planar PV solar panels of the prior art, single axis tracking increases annual output by approximately 30% whilst adding the second axis adds approximately a further 6%. As such only single axis tracking is typically employed with such solar panels. However CPV systems typically position the PV cells at or near the focal point of the optical train such that the increased complexity of two axis or altitude-azimuth tracking is required. Control of the tracking is generally dynamic, i.e. monitoring the solar signal within the optical train, passive by exploiting solar energy, or so-called chronological tracking wherein control is preprogrammed day-time variations.
The selection of control and tracking mechanism is also determined in dependence of the concentration. For example so-called low concentration systems, solar concentration of 2-100 suns, typically have high acceptance angles on the optical train thereby reducing the requirements for control/tracking. Such low concentration systems (LCPV) typically do not require active cooling despite the increased operating temperature of the PV cells which increases with effective number of sun concentration. Medium concentration systems (MCPV), 100-300 suns, require solar tracking and associated control plus more cooling and hence introduces complexity. High concentration systems (HCPV) employ concentrating optics consisting of dish reflector or Fresnel lenses that achieve intensities of 300 suns or more. As such HCPV systems require high capacity heat sinks and/or active temperature control to prevent thermal destruction and to manage temperature related performance issues.